Low power consumption is an increasingly important parameter for microcontroller systems. The wakeup time from a power saving mode is also an important parameter. Various components of the system can add to the time for the system to exit a power saving mode. For example, a memory module can increase the wakeup time from a power saving mode by waiting on a reference current source to reach a target reference current, which can vary depending on temperature or other environmental conditions or both.
Conventional systems rely on a system clock to determine how long it takes a reference current source to reach a target reference current. The length of time to wait for the reference current source is fixed based on a maximum estimated time for reaching the target reference current.